Вкладки в заголовке окна

LRESULT OnDrawCaption(HWND wnd; HRGN rgn) {
    HDC DC;
    // DC = GetWindowDc(wnd);
    if (rgn<>NULL) {
        DC = GetDCEx(wnd, rgn, DCX_WINDOW | DCX_INTERSECTRGN);
    } else {
        DC = GetDCEx(wnd, NULL, DCX_WINDOW);
    }
    TextOut(DC, 130, 2, 'Hello!', 6);
    TextOut(DC, 290, 20, 'Hello!', 6);
    ReleaseDC(wnd, DC);
    return 0;
}
 
LRESULT CALLBACK WndProc(...) {
    switch(uMsg) {
        case WM_CREATE:
            DWMNCRENDERINGPOLICY ncrp = DWMNCRP_DISABLED;
            DwmSetWindowAttribute(wnd, DWMWA_NCRENDERING_POLICY, &ncrp, sizeof(ncrp));
            return 0;
        case WM_NCPAINT:
            HRGN rgn = (HRGN) wParam;
            return OnDrawCaption(wnd, rgn);
        case WM_NCACTIVATE:
            OnDrawCaption(wnd, NULL);
            return (LRESULT) TRUE;
        case WM_DESTROY:
            // ...
            return 0;
    }
    return DefWindowProc(...);
}

        case WM_CREATE:
            DWMNCRENDERINGPOLICY ncrp = DWMNCRP_DISABLED;
            DwmSetWindowAttribute(wnd, DWMWA_NCRENDERING_POLICY, &ncrp, sizeof(ncrp));
            return 0;

        case WM_CREATE:
            BOOL ancp = TRUE;
            DwmSetWindowAttribute(wnd, DWMWA_ALLOW_NCPAINT, &ancp, sizeof(ancp));
            return 0;